The present invention relates to an improved operational lever for a bush cutter, which is locked not only when an engine of the bush cutter is idled but also when a throttle valve of a carburetor provided on the engine is half-opened, such that a human operator comfortably operates the lever.
Known operational levers for bush cutters having prime movers include throttle levers for controlling amounts by which throttle valves are opened, and lock levers for limiting movements of the throttle levers. One example of such operational levers is disclosed in Japanese Patent Laid-Open Publication No. HEI 2-163427 entitled xe2x80x9cTHROTTLE APPARATUS FOR INTERNAL COMBUSTION ENGINExe2x80x9d.
The disclosed apparatus suitable for use on a bush cutter includes a first lever connected via a wire to a throttle valve of a carburetor of an internal combustion engine of the cutter, a second lever pivotable together with the first lever, and a safety lock lever for locking the second lever in place when the throttle valve is opened to such an extent as to idle the engine. The second lever has an adjustment screw abutting on the first lever.
As discussed above, the safety lock lever locks the second lever in place when the throttle valve is opened to idle the engine, such that a human operator can not operate the second lever. When cutting bush, the operator moves the first and second levers to respective intermediate positions in which the throttle valve is half-opened to operate the engine at a given engine speed. To perform the cutting operation maintaining the given engine speed, the operator should hold the second lever in the intermediate position by her or his fingers. While holding the second lever in the intermediate position, during the cutting operation, the operator should also orient the bush cutter in various directions to cut bushes. What has been needed is an operational lever including first and second levers both designed to be held in the respective intermediate positions, such that the operator can comfortably perform the cutting operation.
An object of the present invention is to provide an operational lever for a bush cutter including a throttle lever for opening and closing a throttle valve of a carburetor provided on an engine of the bush cutter, and a lock lever for holding the throttle lever in place not only when the engine is idled but also when the throttle valve is half-opened, thereby imposing a reduced burden of operating the lever on a human operator.
According to an aspect of the present invention, there is provided an operational lever for a bush cutter including an operational rod, a prime mover mounted at a rear end of the operational rod, a cutting blade mounted at a front end of the operational rod, the cutting blade being driven by the prime mover, the operational lever comprising: (A) a handle extending from the operational rod substantially at right angles thereto; (B) a pivotable throttle lever for adjusting an amount by which a throttle valve of the prime mover is opened, the throttle lever having a first handle mounting portion attached to the handle; (C) a first spring for urging the throttle lever in a first direction to close the throttle valve; (D) a pivotable lock lever having a second handle mounting portion attached to the handle; and (E) a second spring for urging the lock lever in a second direction opposite to the first direction; the throttle lever including: (a) a cable connection arm extending from the handle mounting portion and being connected to the prime mover through a throttle cable; (b) a throttle lever operational portion extending from the first handle mounting portion in a direction substantially perpendicular to the cable connection arm; and (c) a protrusion portion extending from the throttle lever operational portion in substantially parallel to the cable connection arm; the lock lever including: (axe2x80x2) a lock lever operational portion extending from the second handle mounting portion; and (b) a lock arm portion extending from the second handle mounting portion in a direction substantially perpendicular to the lock lever operational portion, the lock arm portion being opposed to the protrusion portion of the throttle lever; the lock arm portion having a side protrusion portion formed at an end thereof, the side protrusion portion projecting sideways of the lock arm portion; the protrusion portion moving in a first line as the throttle lever pivots, the side protrusion portion moving in a second line as the lock lever pivots, the first line and the second line intersecting, such that when the lock lever remains urged in the second direction, the throttle lever is prevented from pivoting in the second direction, when the lock lever pivots in the first direction, the throttle lever is allowed to pivot in the second direction, and when the lock lever pivots back in the second direction after the throttle lever pivots in the second direction, the side protrusion portion engages the protrusion portion to prevent the throttle lever from pivoting back in the first direction.
The protrusion portion and the lock arm portion are disposed such that the first line and the second line intersect. If an operator attempts to turn the throttle lever when the lock lever does not pivot but remain urged by the second spring in the second direction, the end of the protrusion portion comes into abutment on the end of the lock arm portion. The throttle lever is therefore prevented from pivoting in the second direction. When the lock lever pivots in the first direction, the throttle lever is allowed to pivot in the second direction. When the lock lever pivots back in the second direction after the throttle lever pivots in the first direction, the protrusion portion of the throttle lever and the lock arm portion of the lock lever are pressed against each other under resilient forces of the first and second springs to thereby prevent the throttle lever from pivoting back in the first direction.